300 PLANT LIFE. 



The Arctic alpine flora is entirely confined to the 

 exposed windy summits of the highest hills in the 

 country. The plants rarely exist below 1400 feet in 

 Southern Scotland. 



On the other hand, in Scandinavia they occur n-ear 

 sea-level, and the circumpolar Arctic flora is entirely 

 composed of some of these plants, and of closely allied 

 forms. They all possess special adaptations, by means 

 of which they can endure the snow of winter, the very 

 short hot summer (sometimes only six weeks in length), 

 and the incessant storms of wind and rain to which they 

 are subjected, on the bare and desolate mountain 

 peaks which they inhabit. 



One characteristic feature comes out very distinctly 

 if we compare closely allied species, of which some are 

 alpine and the others lowland forms. Alcheviilla alpina 

 differs from Alcheinilla vtdgaris chiefly in the leaves. 

 These are of a silvery white colour, due to a dense 

 covering of hairs. Cerastiuin alpinuin again is thickly 

 covered with beautiful white down, whilst the lowland 

 Mouse-ear CMckweed is either glabrous, that is entirely 

 without hairs, or its hairs are of a totally different 

 character. This is a specially good example, for there 

 is a variety of Cerastium triviale^ var. alpestre^ which 

 is much more hairy than the ordinary form, and this 

 also is found high up in the mountains. 



It may be considered proved that these hairs prevent 

 the water from escaping too rapidly from the leaves, or, 

 in other words, that they diminish transpiration. The 

 plant, in fact, develops a coating of hairs to keep in the 

 water. The same Cerastium also illustrates a very 

 well-known characteristic of alpine flowers, which are 

 generally much larger and more conspicuous than those 

 of the lowland species. The flowers of C. alpinuin^ of 



